Refrigeration



June 28, 1938. H. M. ULLSTRAND REFRIGERATION Filed Feb. 6, 1937 3 Sheets-Sheet 1 lulaATTORNEY.

June 28, 1938. ULLSTRAND 2,122,361

REFRIGERATION Filed Feb. 6, 1937 3 Sheets-Sheet 2 MATTORNEY.

June 28, 1938 H. M. ULLSTRAND REFRIGERATION 3 Sheets-Sheet 3 Filed Feb. 6, 1937 A670 2 W WRNEY.

Patented June 28, 1938 UNITED STATES PATENT OFFICE REFRIGERATION Delaware Application February 6, 1937, Serial No. 124,354

4 Claims.

My invention relates to refrigeration, and more particularly to evaporators or cooling units for refrigeration apparatus.

In refrigerators, particularly of the househol type, the evaporator or cooling unit is arranged in a thermally insulated storage space and provides refrigeration both for making ice cubes and the like and for maintaining the 'air in the space at a desired low temperature for properly preserving foods.

It is an object of my invention to provide an evaporator or cooling unit which will eifectively conduct heat from trays adapted to contain water to be frozen and will also present an emcient heat transfer surface for cooling air flowing in contact therewith. I accomplish this by providing a metallic body which is so formed that the heat conductive path between a part utilized for cooling air in a storage space and a part employed for freezing is sufliciently small so that a temperature differential is maintained between these parts which will insure maximum thermal efficiency of the cooling unit.

The above and other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings of which Fig. 1 diagrammatically illustrates refrigeration apparatus provided with a cooling unit or evaporator embodying the invention; Fig. 2 is a top plan view of the cooling unit shown in Fig. 1; Fig. 3 is a vertical sectional view taken on lines 3-3 of Figs. 2 and 5 respectively; Fig. 4 is a sectional view taken on line 4-4 of Fig. 3; Fig. 5 is a front perspective view of the cooling unit shown in Figs. 1 and 2; and Fig. 6 is a vertical sectional view taken on line 6-6 of Fig. 3.

Referring to Fig. 1, I have shown my improved cooling unit or evaporator ill in connection with refrigeration apparatus of a uniform pressure absorption type and like that described in application Serial No. 53,376 of H. M. Ullstrand and A. R. Thomas, flied December 7, 1935. The refrigeration apparatus comprises a generator ll having a partition I! provided with an opening I3 to provide communication between a forward chamber l4 and a rear chamber l5 which is connected to an analyzer vessel It. The generator ll contains a body of absorption liquid, such as water, having a suitable refrigerant, such as ammonia, in solution therein. I

The generator ll may be heated in any suitable manner, as by a gas burner ll, which projects its flame into the forward end of a hori- 55 zontal flue l8 which extends through the generator. V, A suitable combustible gas is delivered from a source of supply through conduit i9 to the burner I1, and the flow of gas to the latter may be controlled by a control valve 20 which is connected by a tube 2i to a thermal bulb or 5 element 22 secured to and in thermal contact with the cooling unit Ill.

The heat applied to the generator ll causes ammonia vapor and absorption liquid to pass through an opening 23 at the lower end of a 10 'conduit 24 which constitutes a vapor-lift and conducts ammonia vapor and absorption liquid into the'upper part of a stand-pipe or separator 25. The liberated ammonia vapor entering the stand-pipe 25 flows downward through a 15 vertical conduit 26 into the analyzer l6 and, together with the ammonia expelled from solution in the generator ll, flows upward to an aircooled condenser 28. The ammonia is liquefied in the condenser 28 and flows through a con- 20 duit 30 and conduit 55-into the upper section of the cooling unit lll which is arranged in a thermally insulated storage space 3|.

An inert gas, such as hydrogen, enters the lower section of the cooling unit it! through a eon- 25 duit 51 from the outer passage 32 of a gas heat exchanger 33. The liquid ammonia evaporates and diifuses into the hydrogen with consequent absorption of heat from the cooling unit In and its surroundings. The resulting mixture of am- 30 monia and hydrogen, that is, gas rich in am- 'monia, flows downward from the upper section of the cooling unit Ill through conduit 55 and the inner passage or conduit 34 of the gas heat exchanger 33 which is connected at its lower end 5 to the upper partof a vessel 35. The gas rich in ammonia flows from the vessel 35 into the lower end of an air-cooled absorber 33 in which i the ammonia is absorbed into weak absorption liquid that enters the upper part of the absorber through a vertically extending conduit 31. The hydrogen, which is practically insoluble and weak in ammonia, flows upward from the absorber 36 through a conduit 38 and the outer passage 32 of the gas heat exchanger 33 into the lower section of the cooling unit Ill.

The absorption liquid flowing downward through the absorber 36 becomes enriched in ammonia and flows into the vessel 35 and thence through the outer passage 40 of a liquid heat exchanger and the analyzer l6 into chamber i5 of the generator ll. Liberated ammonia vapor and absorption liquid are caused to' flow upward through the vertical conduit 24 into the upper part of the stand-pipe 25 to a higher level than it is in the absorber 36, and the absorption liquid weak in ammonia flows from the stand-pipe 25 through the inner passage or conduit 4| of the liquid heat exchanger and conduit 31 into the upper end of the absorber 36.

The lower end of the condenser 28 is connected by a conduit 42, vessel 43, and conduit 44 to the gas circuit, so that any hydrogen which may pass through the condenser can flow to the gas circuit and not be trapped in the condenser. If ammonia is not liquefied in the condenser due to an increase in air temperature, the ammonia vapor will flow through conduit 42 to displace hydrogen in the vessel 43 and force hydrogen through conduit 44 into the gas circuit, thereby raising the total pressure in the system so that an adequate condensing pressure is obtained for the increased air temperature.

In accordance with this invention, the evaporator or cooling unit l9 comprises a looped coil or conduit 45 which is arranged in good thermal relationwith a metallic body having a top wall 46, bottom wall 41, side walls 48, and spaced shelves 49 and 50 extending between the side walls 48. The coil 45 is formed to provide a plurality of U-shaped loops 5|, one of which is shown in Fig. 4, the loops being disposed one above the other with the closed ends of the loops at the forward end of the cooling unit III.

In order to effect efficient heat transfer between the metallic body and the coil 45, the

-walls and shelves are cast about the loops 5| with the loops positioned at the under sides of the top and bottom walls 46 and 41 and the shelves 49 and 56. Figs. 3 and 6, the sides of the loops 5| extend along the side walls 48 and the closed ends extend across the forward open end of the cooling unit Ill. The bends 52 between successive loops 5| are formed on opposite side walls 48 which extend or project beyond the rear of the top and bottom walls 46 and 41 and the shelves 49 and 59. The projected side walls 48 are cast about half the circumference of the conduit 45 at the bends 52, as shown at 53 in Fig. 4.

The upper .end 54 of the pipe 45 is adapted to be connected to the conduit 55 which is connected at its other end to the inner passage 34 of the gas heat exchanger 33, and the lower end 56 thereof is adapted to be connected to the conduit 51 which is connected at its other end to the outer passage 32 of the gas heat exchanger. The under side of the bottom wall 41 of the cooling unit is provided with a sleeve 58 having an opening to receive the thermal bulb 22 of the expansible fluid thermostat.

The shelves 49 and 50 and the bottom wall 41 are adapted to receive trays containing water to be frozen. The evaporation and diffusion of ammonia into the hydrogen within the conduit 45 takes place with consequent absorption of heat from its surroundings, as explained above. When the trays are positioned in the cooling unit,

therefore, heat is removed from the bottom of the trays through the shelves 49 and 59 and -bottom wall 41 which are in thermal relation with conduit 45. The shelves 49 and 50 and the bottom wall 41 are provided with central openings 59 to permit water to drain therefrom when the cooling unit In is being defrosted. A tray or pan (not shown) may be arranged below the cooling unit to collect water formed during such defrosting periods.

In order to provide an extensive heat transfer surface for cooling air in the storage compart- As shown most clearly intween the latter and the, top wall 46.

ment, the top wall 46 of the cooling unit is formed with a plurality of spaced upward extending cooling fins 69 of the general shape shown in Figs. 5 and 6. The uppermost loop 5| of the conduit 45, which is located at the top wall 46, is utilized to cool the top wall and the fins formed integrally therewith, whereby air circulating over these surfaces is cooled and maintained at a desired low temperature.

It will now be understood that the upper part of the cooling unit is primarily utilized for cooling air in the storage compartment and that the remaining or lower part is employed to provide refrigeration formaking ice cubes and the like. The air in the storage compartment is preferably maintained at a desired low temperature which is above freezing while trays containing water or the like positioned in the cooling unit must be cooled to a temperature which is below freezing. Since the upper part of the cooling unit I9 is formed with cooling fins to provide an extensive heat transfer surface, the temperature of the uppermost loop of the conduit 45 will be higher than the temperature of the other loops 5| located at the shelves 49 and 50 and bottom wall 41. With the loop 5| located at the shelf 49 at a lower temperature than the uppermost loop 5|, the ability of the loop 5| at the shelf 49 to produce refrigeration for making ice cubes and the like is impaired in that this loop of the conduit 45'tends to elTect removal of heat from the cooling fins 60 and the top wall 46.

In order that as great a temperature differential as possible will be maintained between theloops 5| located at the shelf 49 and the top wall 46, the side walls 48 are formed with elongated slots or openings 6| which. are parallel to the shelf 49 and at a region forming a boundary be- By providing the slots 6| the heat conductive path between the shelf 49 and top wall 46 is reduced considerably, whereby the loop 5| located at the shelf 49 effects less withdrawal, of heat from the upper part of the cooling unit "I. In this manner the loop 5| at the shelf 49 is maintained at a lower temperature and the removal of heat from a tray positioned thereon is effected more rapidly to hasten the production of ice cubes and the like. Not only is the temperature of the loop 5| at the shelf 49 maintained ata lower. temperature by providing the slots 6|, but the temperature of the cooling fins 60 and top wall 46 is such that air circulating in the storage space is maintained at a desired value above the freezing temperature. It will therefore be understood that by making the heat conductive path sufficiently small between the part of the cooling unit utilized primarily for cooling air and the part employed for producing ice cubes and the like, a higher temperature differential is maintained between these parts than would otherwise obtain, and the thermal efficiency of the cooling unit is improved.

While a particular embodiment of the invention has been shown and described, such variations and modifications are contemplated as fall within the true spirit and scope of the invention, as pointed out in the following claims.

I claim:

1.An evaporator comprising a coil having a plurality of spaced loops disposed one above the other, a metallic body having top, bottom and side walls, and shelves extending between said side walls, a plurality of fins extending vertical- 1y upward from said top wall, said body being 76 cast about said coil so that said loops are located at said top wall and said shelves, at least one of said side walls having horizontally elongated opening between said top wall and the uppermost shelf directly beneath said top wall to reduce the heat conductive path between said top wall and said loop located at said uppermost shelf.

2. A cooling element for a refrigerator comprising a unitary metal casing containing refrigerant passages and having side walls and forming a freezing compartment for ice trays or the like, the upper part of said casing having more extensive heat transfer surface for cooling air than the lower part, and openings in said side walls intermediate said upper and lower parts to reduce the heat conductive path therebetween. I

3. A cooling element as set forth in claim 2 in which said casing is formed by casting metal and the refrigerator passages are formed by a coil cast as an insert.

4. In a cooling element for a refrigerator, a metal casing having side walls and forming a freezing compartment for ice trays or the like, said side walls having openings suitably located and of suflicient size to materially reduce the heat conductive path between the upper and lower parts of-said casing, one of said parts having a greater extent of heat transfer surface for cool- HUGO M. ULLS'I'RAND. 

